Means for automatically defrosting refrigerating units



July 4, 1933. c. T. HOFFMAN 1,916,315

MEANS FOR AUTOMATICALLY DEFROSTING REFRIGERATING UNITS s Sheets-Sheet 1 Filed July 3, 1929 Jwventoz July 4, 1933. c. T. HOFFMAN MEANS FOR AUTOMATICALLY DEFROSTING REFRIGERATING UNITS 3 Sheets-Sheet 2 Filed July 3, 1929 July 4, 1933. Q HOFFMAN 1,916,315

MEANS FOR AUTOMATICALLY DEFROSTING REFRIGERATING UNITS Filed July 3, 1929 3 Sheets-Sheet 3 r0 MOTOR 0F REFRIGERAT/NG APPARATUS.

[/0 V. CURRENT SUPPLY Patepted July 4, 1933 UNITED STATES PATENT OFFICE CHARLES THOMAS HOFFMAN, OF WASHINGTON, DISTRICT OFCOLUMBIA, ASSIGNOR OF ONE-HALF TO EMORY L. GROFF, OF WASHINGTON, DISTRICT OF COLUMBIA MEANS FOR AUTOMATICALLY DEFROSTIN G BEFBIGERATING UNITS Application filed July 3,

This invention relates to refrigeration, and more particularly to a novel and practical means for auton'iatically defrosting the refrigerating unit at predetermined intervals.

It is well known that .the refrigerating units or cooling coils of automatic electrical refrigerators of the type now generally in household use, become coated with frost or ice which must be permitted to melt away at intervals to preserve the eflicicncyof the box. According to the present practice it is customary to manually cut olf the current supply to the motor of the refrigerating apparatus and temporarily allow the box to stand until the frost or ice melts from the refrigerating unit whereupon it is necessary manually to restore the circuit to the motor and compressor to again start the freezing cycle. The defrosting of refrigerators is more or less of a nuisance especially in household refrigerators where the user has the impression that all of the functions and operations of the machine are auiomatic. Some users might be disposed to promptly and periodically defrost While others might allow too much frost or ice to form and consequently not only reduce the efficiency of the box but perhaps cause other damage and inconvenience.

Accordingly, the present invention contemplates simple, practical and reliable means for temporarily breaking the circuit to the motor of the refrigerating apparatus until the ice or so-called frost has melted away whereupon the. circuit will be automatically restored and the box again put in operation without requiring manual attention.

A primary object of the invention is to provide a device including a novel circuit and circuit controlling means which is operated by direct contact or engagement with the frost or ice forming on the fins or other part of the refrigerating unit.

Another object of the invention is to provide means for visually indicating occurrence of the defrosting operation.

A further object of the invention is to provide a construction which will be safe and in every way meet underwriters requirements both as (o the type of switches involved 1929. serial n. 375,647.

and the means for closing the circuit so that no arcing or sparking will occur during the operation of the device. 7 Also, in that connecti on the invention contemplates the use of electrical devices in which no current is allowed to flow except for an instant at the beginning and end of the defrosting cycle.

A still further object of the invention is to provide means for controlling or setting the circuit closing means in such a way that more or less ice or frost may be permitted to form before the circuit is closed thereby enabling the user to time the defrosting cycle accurately so that he will not only know how often the defrosting operation will occur but inthe event that it should occur at an undesirable time the cycle can be changed easily and without difliculty so as to delay defrosting at a particular time, thereby giving the user complete control of the defrosting cycle in a simple and practical manner.

With the above andother objects in View the invention consists in the novel features of construction, combination and arrangement of parts as will be hereinafter more fully described, illustrated in the accom panying drawings and defined in the appended claims.

-A preferred and practical embodiment of the invention is shown in the accompanymg drawings, in which:

Figure 1 is a diagrammatic view illustrating the circuit arrangement and the mechanical devices operated in conjunction therewith, the parts being shown in psition about to start the defrosting cycle.

Figure 2 is a view similar to Figure 1 showing the position of parts during the defrosting cycle and with the circuit controller of the device about to restore the refrigeratmg circuit.

Figure 3a is a detail vertical sectional view of the circuit controller.

Figure 3 is a detail view of the circuit controller which contacts with the ice.

Figure 4 is a detail sectional view taken on the line 4-4 of Fig. 1.

Figure 5 is a detail view of the terminal changing switch.

Figure 6 is a diagrammatic view illustrat- 5 defrosting circuit.

Similar reference characters designate corresponding parts throughout the several figures of the drawings.

In carrying the invention into effect it is proposed to provide a simple and compact arrangement that will reliably function under all conditions and use, and which Wlll be controlled directly by the frost or ice forming on the fins or elsewhere and by box temperature at the end of the defrosting cycle. That is to say, when ice builds up to a certain height or depth on the cooling unit, the circuit will become automatically closed to cut off the supply of current to the motor; of the refrigerating apparatus, and as soon as the ice melts and the temperature of the box rises, the circuit will be automatically restored.

Referring to the drawings, the present invention comprises in its organization a defrosting control unit including a circuit controller or switch A adapted to directly contact with the ice, the same being mounted on an arm B pivotally supported on a shaft or axis C which also carries a base D on which other elements of the unit are mounted so that when the position of the arm B is ad- 'usted through the means of the device E to ring the circuit closer or switch A a greater or less distance from the cooling coil or fin,

cle and then again for an instant .at the end of the defrosting cycle so that no current is flowing through any part of the apparatus except for a short time at the periods referred to. The electromagnet M operates in conjunction with an armature element designated generally as N which in turn alternately operates first one and then the other;

of a pair of dogs 0 and O which are adapted to engage the actuator lever F on opposite sides of its center at alternate reciprocations of the armature member N thereby to snap;

the actuator F from the position shown in Fi ure 1, for example, to the position shown in Figure 2 and back again according to the conditions controlled by the circuit controller A.

With the parts shown in the osition in Figure 1, the switch S of the re rigerating circuit is closed, but the instant that the ice formation comes into sufiicient proximity or touches the casingof the circuit cont-roller A, the control circuit will be operated to cause the actuator F to pull away from the terminals of the switch S of the refrigerating circuit and break the circuit. The arm B will then be pulled toward the ice formation on the cooling coil with a relatively light pressure so that as the ice melts, the I circuit controller A will follow the same until it reaches the fin of the cooling unit or of the casing, which ever it ,might be.

lVhile the actuating arm F is in defrosting position, that is with the switch S open, it

closes an indicator circuit R to visually show all the operating parts of the device may be fthat the refrigerator is defrosting.

likewise adjusted to insure the proper functioning of the arm B. It will, of course, be understood that the purpose of adjusting the circuit controller A is to control the timing of the defrostin cycle, that is to say, the timing of the de rosting cycle can be shortened or lengthened according to the depth of the ice formation on the cooling unit by setting the circuit controller A at a greater or less distance from the part on which the ice forms.

The circuit controller A is intended and adapted to control what may be termed a defrosting circuit as distinguished from the refrigerating circuit which includes the line wires a: and 3 leading to the motor of the usual refrigerating apparatus, and the wire 1 having therein a master switch S which is opened and closed by' an actuator element desi ated generally as F. This element is pre erably. pivoted on'the axis or shaft C and has connected to one end thereof a spring G whose op osite end is connected to a switchlever g} pivoted to the arm .B as indicated at I and carrying therewith a contact member K adapted to alternately enga e with contacts L and L to close the circult to an electro-magnet M, first for an instant at the beginning of the defrosting cytion 3a which fits over the stud 11; an

G to move the arm upwardly and reset the same for the next refrigerating cycle while simultaneously restoring the refrigerating circuit through the closing of the switch S.

Referring more specifically to the details of construction, which, of course, may be varied within the scope of the invention, reference will first be made to the circuit controller.

This device is preferably of the spring thermostat thermometer type and includes a suitable casing 1 having the front wall 1a which contacts with the ice made of metal. This wall carries therewith a stud 16 on its inner face on which the arm or pointer 2 and its shaft 3 are rotatably mounted. The shaft 3 preferably consists of a metallic oran insulated portion 3?) which is secured to the end of the shaft 3 by means of a fastening 3c. The thermostat spring l has one end anchored to the metallic plate 1a and the opposite end anchored to the shaft 3 and said spring is intentionally mounted on the plate 10 so that cold may be better conducted to the spring 4 to render the action of the coil and the arm 2 more positive when the ice strikes or extends into close proximity to the plate 11:. The arm 2 which is moved by the thermostat member 4 is adapted to cooperate with contacts 5 and 6 carried by the casing 1 but insulated therefrom in any suitable manner. These contacts are preferably adjustable, that is they may be placed closer together or farther apart on the line of the are described by the end of the arm 2. The contact 5, for example, is intended to be engaged b the arm 2 when the iceformation on the coo ing unit U extends into close proximity to or touches the member 1a of the easing 1, and on the other hand when the ice melts away, and the temperature of the box rises, the thermostat coil 4 will move the arm 2 into engagement with the contact 6.

The contact 5 is connected by a wire 50 with the terminal L of the terminal changing switch which includes the lever H, and the contact 6 is connected by the wire or other conductor 6a with the terminal L of said switch. The contact member K of the terminal changing switch H is electrically connected by the wire 9 with one terminal of a dry rectifier 10. This rectifier may be of any standard type now available on the market such as a Kodel or Elkon rectifier whose terminals are connected with a step-down transformer 11 which is in turn connected to a source of 110 volt A. C. supply. The purpose of this transformer and rectifier is to furnish a low voltage direct current, when temporarily required, to the electro-magnet M and to that end the said electro-magnet is included in circuit with the rectifier by the wire 12. The said electro-magnet is also connected by the wire or other conductor 13 directly with the arm 2 of the circuit controller A. Therefore, as the arm 2 moves from one side to the other, under changing temperature conditions, the circuit will be automatically and temporarily closed through the electro-magnet M according to which one of the contacts L and L is engaged by the contact member K.

To prevent any arcing or sparking incident to the making and breaking of the circuit in the terminal changing switch H a condenser 14 may be connected across the lines 9 and 13. Any tendency to produce a spark in the switch H will, therefore, be absorbed by the condenser action.

Each time the electro-magnet M is energized, that is at the beginning and at the end of the defrosting cycle, due to the closing of the circuit first by the arm 2 engaging with the contact 5 and then by the arm 2 engaging with the contact 6, the armature ele engaged by the ment N will be moved or lifted. This armature member is preferably slidably guided in a bracket 15 mounted on the base D and is maintained in its normal position, that is, away from the electro-magnet M by a spring 16 confined between the bracket 15 and the head 17 which is ada )ted to engage alternately with the dogs and 0.

As previously indicated the said dogs 0 and O are carried by the arm B in any convenient and suitable manner. For example, the said dogs have their shank portions 18 mounted in suitable guides 19 so that their shanks will not turn, said guides being carried by the arm B and provided with the abutments 20 against which the springs 21 act to maintain the dogs in their normal position. The lower ends of the dogs may be provided with the angular or equivalent portions having the offset fingers 23 for engaging with the actuator lever F.

With the arrangement of the dogs 0 and 0 shown in the drawings, it will be apparent that the hooked ends 24 thereof are adapted to be alternately moved or swung into the path of movement of the head 17 of the armature element N. That is to say, as shown in Figure 1, when the circuit controller A is about to close the circuit by engaging with the contact 5, the dog 0 will have its hooked portion 24 in position to be head 17 of the armature member. When the defrosting circuit, which includes the circuit controller A and the term'nal changing switch H is closed the armature element N will be pulled toward the electro magnet M, thereby pulling the dog O with it so that the finger 23 of the dog w1ll move the actuator lever F against the tension of its spring G until the lever is moved past center and the spring G will snap the actuator lever F to the position shown in Figure 2, thereby breaking the circuit between K and L but leaving the arm B under tens1on of the spring G so that the circuit controller A will follow the ice formation toward the cooling unit.

It will of course be apparent that when the dog 0' moves the actuator F, the refrigcrating circuit will be broken by the openmg of the master switch S, due to the fact that the conductor element 25 on the actuator F will leave the terminals of the master switch and thus open or break the refrigeratmg circuit.

When the box temperature rises due to the melting of the ice the arm 2 will move toward the contact 6 of the circuit controller A. Vhen the arm 2 closes the circuit through said contact 6, the defrosting circuit is then again closed with the parts in the position shown in Figure 2, whereupon the dog 0 will be moved bv the armature element N thereby to cause said dog to move the actuator F back to the position of Figure 1 whereupon the III) arm B will be set to its originalposition and also the actuator F will close the master switch S and restore the "refrigerating circuit.

As previously explained, when the apparatus is in defrosting position, an indicating circuit R will be closed due to the fact that the contact strip 26 on the actuator F bridges the terminals of the indicator switch R. In the example shown, when the circuit is closed in the indicating circuit R the lamp R is illuminated. However, of course, it will be understood that any form of visual indicator may be used for giving notice to the user of the box that the refrigating circuit is open or broken and that the defrosting period is on or 0d. 7

Referring to the means for ad usting the position of the circuit controller A, namely the unit E, it will be observed that the same includes a manually adjustable screw 27 having a finger nob 28 and operating through a suitable bracket 29 supported on a ,wall or other part independent of the'base D which carries the electro-magnet and other parts. This screw may be provided with an indicating wheel 30 which may be calibrated to indicate the relative-adjustment or location of the circuit controller A and is adapted to be held in a set position by a pawl or equivalent element 31. The adjustable end of the screw 27 is preferably provided, with a collar 32 for receiving the end of a bracket arm 83 carried by the base D while the tip end of the screw 34 isadapted to bear against the extension 35 of the arm B. The purpose of this arrangement is to move the circuit controller A closer to or farther away from the cooling unit U and at the same time maintain the proper relative position between the head 17 of the armature and the dogs 0 and O by moving the base on which the armature mounted to the same degree that the arm is moved in one direction or the other. Thus, the dogs 0 and 0 will always be in position to alternately clear the movement of the armature element N'since the original adjustment between the arm and the armature element N is maintained.

One of the advantages of the means described for operating the actuator F, namely the dogs 0 and O is that if the magnet M should be energized unnecessarily or unexpectedly for any reason after the dog has been engaged, further movement thereof Wlll not affect the other dog which must be engaged to throw the actuator to the opposite position. Thus, if an untimed impulse should occur in the line which would tend to actuate the magnet M again the undesired reciprocation of. the armature N'will not affect the dog which is thrown out of position so I that it cannot be engaged by the magnet.

Another advantage ofthe present invention resides in the provision of means which .efiects a material economy in current conment with either of the contacts 5 or .6 and:

immediately upon the breaking of the circuit from either of the contacts .5 or 6 by the terminal changing'switch H the circuit is quicklybroken so that at no time is there any danger of current. from the main linespassing through the defrosting circuit. This prevents heating of any of the units included in the defrosting circuit.

Figure 6 illustrates a modification of the invention shown in Figs. 1 to 5. In all essential particulars, however, the features shown in the figures referred to are thesame. For cxample, the mechanical parts-such as the circuit controller A, carrier arm-B and'actuator F are all mounted on the axis or shaft C, while the dogs 0 and O are controlled by the armature element N and electro-magnet Min the same way that they are in the construction previously described. Also the same type of transformer 11 and rectifier 10 are used. However, the switch operating in conjunction with the circuit controller A and the means for adjusting or setting the positionof the latter with reference to the ice forming surface are different from those previously described.

In the modified arrangement, the switch operating in connection with the device A is designated as H and includes a pair of fixed terminal contacts 36 and 37 which may be relatively long ,arcuate members respectively mounted on the insulated blocks, if desired, which carry the terminals of the switches S and B. These contacts are ada t- ;edto be engaged by the contact 38 carried the circuit being closed to the electromagnet M until the actuator arm is moved past center by the spring G. It is of no consequence that the live contact bridges both contacts at the same time momentarily because the circuit to the receiving contact of this switch is broken or open at the terminal or contact in the circuit controller when the actuator is moving.

Referring to Fig. 6 it will be seen that the contact 38 on the actuator is connected by wire 9a with the rectifier 10. When the parts are'in the position shown and the ice contacts with the circuit controller A, the circuit will be closed through the wire 12a to the electromagnet M, thence through the wire 13a to the arm 2 of the circuit controller from whence it passes through wire 5?) to terminal 36 which is in engagement with the movable contact 38 that is connected to the rectifier by wire 9a. When the box warms up after the ice melts the circuit is again closed by arm 2 engaging contact 6 which is electrically connected by wire 66 with the switch terminal contact 37. The circuit is then closed through contact 38 and wire 9a to the rectifier by wire 9a.

Another feature of this arrangement is that the electromagnet M, armature N and the axis C on which the actuator F and arm B are mounted are all carried by an adjustable base D. This base is mounted for sliding rectilinear movement on a casing part D, as distinguished from an arcuate or partly circumferential movement as in the case of the base or platform D in Figs. 1 and 2. The purpose of this adjustment is to move the circuit controller A to a greater or less distance from the ice forming part of the cooling coil. Referring more in detail to the means of adjustment referred to, it will be seen that the base or platform D carries guide elements 39 which may be provided with slots to receive the shanks of guide studs mounted on the casing part D ,:t-he said studs having clamping heads 40 thereon to engage the members 39 and hold the same in the desired set position.

For the purpose of accurately moving the base D to effect the desired setting of the circuit controller A an adjusting device E is utilized. This device includes a bracket 41 or its equivalent carried by the base and engaged by an adjusting screw 42 having thereon a collar 43 which rides in a guiding element 44 carried by the casing part D". B turning the screw 42 through the medium of the finger knob 45 the base I) may be moved to any extent desired, and in that connection, the dial 46 carried by the shank of the screw may be placed in a more readily accessible and readable position so that the user of the box can conveniently move the entire defrosting unit to readily regulate the position of the circuit controller to adjust the defrosting cycle.

In this arrangement the extension 35a on the arm B is stopped at its extreme limits of movement by engaging with the abutments 366.

In both forms of the invention the circuit controller A is preferably mounted on a self adjusting carrier or support so that it will not only follow uneven ice formation but will also permit sufficient range of movement for the arm B to assure efiicient functioning of the parts actuating the arm.

As will be observed from Fig. 7 the circuit controller A has its casing 1 fitted with a tube 47 which enters a conical hood 48 carried by the arm B. This tube is engaged by a compressible conical spring, 49 which abuts against the collar 50 and which is also anchored as at 51 to the arm B. This construction permits the circuit controller to have both a universal compensating movement for uneven ice on agement and also ermits the arm B to ma e its full forwar stroke or movement by compressing the spring 49, thus always tending to force the circuit controller against the ice formation and insuring it reaching the ice forming part when all the ice has melted.

The switch S in the main current supply line to the refrigerating apparatus is used in addition to the usual thermostat switch which is operated by box temperatures to control the refri erating cycle under normal conditions, and because the socalled defrosting circuit is connected with the source of current supply ahead of the switch S, this circuit .will operate independently of the thermostat control now commonly used on automatic refrigerators.

In connection with the operation of the apparatus disclosed in Figs. 1, 2, and 3, it may be pointed out that with the range of adjustment afforded by the device E, the apparatus functions as a full automatic defrosting means according to the setting of the controller A with reference to the fins, baflies, or other ice collecting surface of the evaporator. That is to say, when the circuit controller A is adjusted or set a spaced distance from the ice collecting surface, said circuit controller will not operate until the ice, builds out to it or is in actuating proximity to it. However, by manually adjusting the device E to take up any space between an initially distant setting from the ice forming surface and the formation of the ice as it may exist, the circuit controller may be manually brought into operation. Therefore, the present construction is capable of functioning both as a full automatic and a semi-automatic apparatus in the sense that it can be manually manipulated to start the defrosting period whenever desired.

Furthermore, it will be apparent that the present mechanism includes a plurality of motor control switches, namely, the switch including the actuator F which cooperates with the motor control terminals S (Fig. 1 or its equivalent) and the thermal cutout or circuit controller A. Also an adjustment control means is provided for the switch mechanism. That is to say, the entire position of the switch FS may be adjusted through the medium of the parts 3233 and the parts 27 and 29. The adjustment of the switch FS and its associated parts also changes the effective position of the thermal cutout A with reference to the evaporator. The entire adjustment control mechanism or means consisting of the parts 27 -29-3033 and the arm 35 is in turn controlled by the unit control knob 28. By turning the knob 28 to its extreme movement in one direction the thermal cutout can be brought into contact With a part of the evaporator. By moving the unit control knob 28 in the opposite direction the thermal cutout can be moved to its maximum position away from the evaporator. Intermediate positions of the unit control knob 28 are effective to place the thermal cutout A at any desired location with reference to the evaporator. By means of the unit control knob 28 it will also be 7 apparent that if the thermal cutout is spaced away from the evaporator, that 1s in an noperative position with reference to the we formation, it can be moved to an operative position by simply turning the unit control knob to bring'the thermal cutout into contact with the ice formation. The reverse of this is also true. I

Without further description it Is thought that'the featuresand advantages of the invention will be readily apparent to those skilled in the art, and it will of course be understood that changes in the form, proportion and minor details of construction may be resorted to, without departing from the sp1r1t of the invention and scope of the appended claims.

I claim:

1. In a refrigerator, the combination with the cooling unit and means for interrupting and restoring the refrigerating cycle thereto, of means adapted to contact with and follow the ice formation on the surface of the cooling unit to automatically control said means for interrupting and restoring the refrigerating cycle. I

2. In a refrigerator, the comblnation with the cooling unit and an element for interrupting and restoring the refrigerating cycle, of means for automatically controlling said element including a device responsive to changing temperature conditions, and means controlled by said device for causing the same to follow the ice formation on the cooling unit during melting and to reset the same after melting.

3. In a refrigerator, the combination with the cooling unit and an element for interrupting andrestoring the refrigerating cycle, of means for automatically controlling said ele-v ment including a device responsive to changing temperature conditions, and means including a spring tensioned member carrying said device for causing the same to follow the ice formation on the cooling unit during melting and to reset the same after melting.

4. In a refrigerator, the combination with the cooling unit and an element for interrupting and restoring the refrigerating cycle, of means for automatically controlling said element including a device controlled by the formation and melting of ice on the cooling unit and responsive to changing temperature conditions and means including a pivoted arm on which said device is mounted, an actuator member, a switch in circuit with said device responsive to changing temperature conditions, a spring operativel connecting the actuating member and swito and means controlled by said device for operating the actuator member.

5. In a refrigerator, the combination with anelement for interrupting and restoring the refrigerating cycle, of means for automatically controlling said element including a device responsive to changing temperature conditions and including a shiftable conductor arm and spaced contacts, a circuit controlled by said device and including the said conductor arm and spaced contacts, a switch in said circuit, an electroma et in said circuit, and means controlled y said electromagnet for operating said switch.

6. In a refrigerator, the combination with an element for interrupting and restoring the refrigerating cycle, of means for automatically controlling said element including a device responsive to changing temperature conditions and including a thermostat controlled conductor arm and spaced adjustable contacts, a circuit controlled by said device and including the'said conductor arm and spaced contacts, a switch in said circuit, an electromagnet in said circuit, and means controlled by said electromagnet for operating said switch.

7. In a refrigerator, the combination with an element for interrupting andrestoring the. refrigerating cycle, of means for automatis cally controlling said element including a device responsive to changing temperature conditions, a pivoted arm on which said device is mounted, an actuator member mounted coaxially with the arm', aswitch, a spring tue element for moving the actuator member.

members carried by said arm and having oifset portions thereon adapted to be engaged by the armature element in its movement,'said dogs being spaced on opposite sides of the axis of the arm whereby they will be alternately thrown into and clear of the path'of movement of said armature element.

9. In an electrical refrigerator a switch for making and breaking the circuit to the refrigerating apparatus, a coolin unit, and means for automatically defrosting the cooling unit and comprising means for operating said switch, said means includmg a defrosting circuit, a circuit controller operated by the formation and melting of 100. on the cooling unit included in said defrosting circuit, a switch also included in the defrostin circuit, and means operated b closing sal defrosting circuit to alternate y operate the switch for making and breaking the circuit to the refrigerating apparatus.

10. In a refrigerator, a master switch for opening and closing the circuit to the refrigerating apparatus, a defrosting devlce including a circuit controller adapted to be actuated by ice and box temperature, an electromagnet, :1 terminal changing switch, a defrosting circuit having the terminal changing switch included therein, and actuating means operated by the electromagnet for. shifting the terminal changing switch.

11. In an electrical refrigerator, the combination with the current supply line to the refrigerating apparatus and a cooling unit, of means controlled by the formation and melting of ice on the cooling unit for opening and closing the circuit in said current supply line.

12. In an electrical refrigerator,- the combination with the current suply line to the refrigerating apparatus and. a cooling unit, of switch means in said supply line, and means operated by the formation and melting of ice on the cooling unit for controlling the said switch means.

13. In an electrical refrigerator, the combination with the current supply line to the refrigerating apparatus and a cooling unit, of means controlled by the formation and melting of ice on the cooling unit for opening and closing the circuit in said current supply line, and means for indicating the defrosting period.

14. In an electrical refrigerator, the com bination with the current supply line to the refrigerating apparatus and a cooling unit, of means controlled by the formation and melting of ice on the cooling unit for opening and closing the circuit in said current supply line, and means for visually indicating the duration of the defrosting period.

15. In an electrical refrigerator, thecombination with a source of alternating current supply for the refrigerating apparatus, a switch for opening and closing the circuit to said refrigerating apparatus, a cooling unit, and a defrosting device including a defrosting circuit, means connected with the source of alternating current supply to furnish direct curent to the defrosting circuit, a circuit controller included in said defrosting circuit and adapted to follow the ice formation on the cooling unit, and means operated by the circuit controller for temporarily closing the defrosting circuit.

16. In a refrigerator, the combination with means for interruptin and restoring the refrigerating cycle an the cooling unit, of means adapted to contact with and follow the ice formation on the cooling unit to automatically' control said means for interruptin and restoring the refrigerating cycle, an means for spacing the means adapted to con,- tact with and follow the ice formation at a greater and less distance from the said ice formation.

17. In a refrigerator, the combination with an element for interrupting and restoring the refrigerating cycle and a cooling unit, of

means for automatically controlling said element including a device responsive to changing temperature conditions, means controlled by said device for causing the same to follow the ice formation on the cooling unit during melting and to reset the same after melting, and means for mounting said device whereby it may have a universal rocking and sliding movement independently of said means for causing the same to follow the ice formation.

18. In a refrigerator, the combination with an element for interrupting and restoring the refrigerating cycle and a cooling unit, of means for automatically controlling said element including a device responsive to changing temperature conditions, means controlled by said device for causing the same to follow the ice formation on the cooling unit during melting and to reset thesame after melting, means for manually setting said device to vary the defrosting cycle, and means for mounting said device whereby it may have a universal rocking and sliding movement ,indepently of said means for causing the same to follow the ice formation and rendering said means for manually setting the device effective under all conditions of use.

19. In a refrigerating system, the combination with the cooling unit, means for circulating a refrigerant medium through said unit and temperature responsive means for said first named means to maintain the unit between predetermined limits of temperature, of means for automatically opening and closing the circuit to said means for maintaining said unit bet-ween predetermined limits of temperature according to the degree of frost formation on the cooling unit and temperature conditions within the refrigerator.

20. In a refrigerating system, the combination with a cooling unit and an element comprising means for circulating a refrigerant medium through said unit and temperature responsive means for controlling said first mentioned means to maintain said unit between predetermined limits of temperature, of means for automatically controlling said element including a device responsive to the differential between ice and box temperature, a circuit controlled by said device, an electromagnet, an armature operatedby said ele ctro-magnet and the latter being included 1n.

said circuit, and means controlled by said armature for automatically making and breaking the circuit controlled by said device.

21. In an electrical refrigerator,-the combination with the current supply line to the refrigerating apparatus including means for circulating a refrigerant medium through an evaporator and temperature responsive means for controlling said first mentioned means to maintain the evaporator between predetermined limits of temperature, of defrosting means arranged in the current supply line anterior to said refrigerating apparatus and controlled by the formation and melting of ice on the evaporator for opening and closing the circuit in said supply line.

22. In an electrical refrigerator, the combination with the refrigerating apparatus including a motor operating switch and an evaporator, and the current supply line to the motor and switch,'of a defrosting switch ,device for opening and closing the circuit in said current supply line, and a thermostat device included in circuit withvsaid defrosting switch and located 'at the evaporator,

, and means for manually causing the operation of said thermostat.

'23. Means for automatically defrosting the refrigerating unit of refrigerators equipped with electrically operated means for circulatinga refrigerant in the unit and means for maintaining said unit within predetermined temperature limits, comprising the combination with thecurrent supply line to said electrically operated means, of means controlled by the formation and melting of ice on said unit for opening and closing the circuit of the current supply line and means for regulating the frequency of defrosting V periods.

24. Means for automatically defrosting the refrigerating'unit of refrigerators equipped with electrically operated means for circulating a refrigerant in the unit and means for maintaining said unit within predetermined temperature limits, comprising the combinati on with the current supply line to said electrically operated means, of means controlled by the formation and melting of ice on said I, unit for opening and closing the circuit of the current supply line, and means for manually setting said last named means to regulate the frequency of defrosting periods. 1

25. Defrosting means for electrically operated refrigerators comprising the combination with the refrigerating apparatus operating within predetermined temperature limits and the current supply line leading thereto, of a main switch for opening and closing the circuit in said current supply line, a circuit controller adapted to be actuated by low and ated switch means thereby to actuate the same high temperature in the refrigerator, electromagnetic means included in circuit with said circuit controller, a terminal changing switch also included in circuit with the electro-ma i netic means, and means actuated by the said electro-magnetic means for shifting the said main and terminal changingswitches.

26. Defrosting means for electrically operated refrigerators, comprising the combination with the refrigeratin apparatus 0 erating within predetermined temperature iimits and the current suppl line leading thereto, of electro-magnetica 1y operated switch, means in said current supply line anterior to the refrigerating apparatus, and a thermostat switch re's onsive to temperature changes in the re rigerator and included in circuit with the electro-magnetically operand control the circuit in said supply line.

. 27..Defrosting means for electrically operated refrigerators, comprising the combination with the refrigerating apparatus operating Within predetermined temperature limits and the currentsupply line, leadin thereto, of electro magnetically 0 rated switch means in said current supp y line, and thermal responsive switch-means in circuit with said electro-magneticallyoperated switch means actuated by the change in temperature occurring at the beginning and end of the defrosting period to control said electro-magnetically operated switch means to open and close the circuit in said current supply line.

28. A method of automatically defrosting refrigerating units of electrical .ice boxes which consists in subjectin a thermal responsive element to the in uence of direct contact with the ice formation on the refrigcrating unit and causing said element to open the circuit to the motor of the refrigerating apparatus and simultaneously close a circuit to an indicating device, or viceversa.

, 29. Means for automatically defrosting the no refrigerating unit of refrigerators equipped with electrically operated means, for circulating a refrigerant in the unit, and means 7 for maintaining said unit within predetermined temperature limits; comprising the combination with the current supply line to said electrically operated means, of a thermal-controlled electro-magnetic switch device included in the said-current supply line for opening the circuit'therein.

30. Means for automatically defrosting the refrigerating unit of refrigerators equipped with electrically operated means for circulating a refrigerant in the unit, and means for maintaining said unit. within predeter mined temperature limits; comprising the combination with the current suppl line to said electrically operated means, 0 a thermal-controlled electro-magnet'ic switch device included in the said current supply line for closing the circuit therein.

31. Means for automatically defrosting the refrigerating unit of refrigerators equipped with electrically operated means for ClIClllating a refrigerant in the unit and means for maintaining said unit within redetermined temperature limits; comprising the combination with the current supply line to said electrically operated means, of a switch device located in said current supply line anterior to the refrigerating apparatus, and thermal-responsive means for operating the switch to control the circuit.

32. In an electrical refrigerator having an evaporator element, a switch in the current supply line to the mechanism for circulatin re rigerant through the evaporator and temperature responsive means positioned to be contacted by the ice formation on the evaporator element and operating to open said switch.

33. In an electrical refrigerator having an evaporator element, a switch in the current supply line to the mechanism for clrculating refrigerant through the evaporator and temperature responsive devices for openlng sa d switch and for closing the same, one of sa1d devices bein positioned so as to be contacted by the ice formation on the evaporator to cause opening of the switch.

34. In an electrical refrigerator havlng an evaporator element, a switch in the current supply line to the mechanism for clrculatlng refrigerant through the evaporator, temperature responsive means positioned to be contacted by the ice formation on the evaporator element and operating to open said switch, and means for adjusting the temperature responsive means relative to the evaporator element.

35. In an electrical refrigerator, an evaporator, a switch in the current supply line, means controlled by the iceformation on the exterior of the evaporator for controlling the operation of said switch, and means for adjusting the last named means relative to the evaporator.

36. In an electrical refrigerator, an evaporator, an electro-magnetic switch in the current supply line, means controlled by the formation of ice on the exterior of the evaporator for controlling the operation of said switch, and means for adjusting the last named means relative to the evaporator.

37. In a refrigerator having an evaporator, means for temporarily suspending the refrigerating cycle of the evaporator to render the same capable of defrosting, means controlled by the formation and melting of ice on the evaporator for controlling said first named means, and means for adjusting the said means controlled by the formation and melting of ice on the evaporator with reference to said evaporator.

38. In a refrigerator having an evaporator, means for temporarily suspending the refrigerating cycle of the evaporator to render the same capable of defrosting, and a movably supported member carrying therewith means for controlling said first named means.

39. In an electrical refrigerator having an evaporator element, means for circulating a refrigerant medium through the evaporator including a motor, a plurality of motor control switches, an adjustment control for one of said switches, and a unit control comprising means for actuating the adjustment control to change the effective position of the latter, said means including a rotatable part operatively associated with the last meng tioned switch.

40. In an electrical refrigerator, an evaporator, means for circulating a refri erant medium through the evaporator inclu ing a motor, means or controlling the motor comprising a switch mechanism, a thermal cutout mechanism, adjustment control means for the switch mechanism, and a unit control comprising a handle for operating the adj ustment control means.

41. In an electrical refrigerator, an evaporator, means for circulating a refrigerant medium through the evaporator including a motor, means for controlling the motor comprising a switch mechanism, a thermal cutout mechanism, adjustment control means for the switch mechanism, and a unit control comprising a knob for operating the adjust ment control means, said unit control also being adapted to render the thermal cutout mechanism effective and ineffective, respectively, the intermediate positions of the knob being effective to change the position of the adjustment control means as desired.

42. In an electrical refrigerator, an evaporator, means for circulating a refrigerant medium through the evaporator including a motor, means for controlling the motor comprising a switch mechanism, a thermal cutout mechanism, adjustment control means for the switch mechanism, and a unit control comprising means for operating the adjustment control, said means being operatively associated with the thermal cutout mechanism for rendering the thermal cutout mechanism operative in one position of the adjustment control means and inoperative in another position thereof.

43. In an electrical refrigerator, an evaporator, means for circulating a refrigerant medium through the evaporator including a motor, means for controlling the motor comprising a switch mechanism, a thermal cutout mechanism, and a unit control comprising means for actuating the adjustment control, said means being operatively associated with the thermal cutout to render the same effective from an ineffective position.

unit, when said coating reaches a predeter- 44. In an electrical refrigerator, an evaporator, means for circulating a refrigerant medium throu h the eve orator including a motor, means Eor control ing the motor com- 5 prising a switch mechanism, a thermal cutout mechanism, an adjustment control means for the switch mechanism, and a unit control comprising a knob for actuatin the adjustment control means, said knob eing operatively associated with said thermal cutout to render the same operative and inoperative in different positions of the knob.

45. In an electrical refrigerator, an evaporator, means for circulating a refri erant medium through the evaporator inclu ing a motor, means or controlling the motor comprising a switch mechanism, a thermal cutout mechanism. an adjustment control means for the switch mechanism, and a unit control comprising a control handle for adjusting the setting of the control switch and for rendering the thermal cutout mechanism inoperative and ready for operation in one position of the control handle.

46'. Means for causing defrosting of a coolng unit in power refrigerating apparatus, including; a control member adjacent the cooling unit, said member adapted to be engaged by the coating of ice on the cooling mined thickness, and means operated on contact of'the ice coating with the controlling member for shutting ofl the power to the refrigerating apparatus.

47. A refrigerating system comprising means for starting and stopping a refrigerator at definite temperature limits successively for a plurality of cycles, and an automatic means for increasing the starting temperature to a defrosting temperature for a defrosting cycle after the said plurality of cycles.

48. A refrigerating system, comprising in combination a cooling element normally maintained at desired refrigerating temperatures, and means rendered operable automatically at intervals by the normal operation of the system to permit rise of the temperature of the cooling element to a defrosting temperature limit.

49. The method of automatically controlling frost formation on cooling units of refrigerators, which consists in maintaining a normal refrigerating cycle within predetermined limits to provide frost producing temperatures, and then automatically modifying the refrigerating cycle to produce frost melt ing temperatures.

50. The method of automatically controlling frost formation on cooling units of refrigerators, which consists in maintaining a normal refrigerating cycle within prede termined limits to provide frost producing temperatures, then automatically modifying the refrigerating cycle to produce frost melting temperatures, and subsequently automatically restoring the normal refrigerating cycle.

51. In an electrical refrigerator, including an evaporator, a switch in the current supply line, and means controlled by the ice formation on the exterior of the evaporator for controlling the operation of said switch.

52. In an electrical refrigerator including an evaporator, an electro-magnetic switch in the current supply line, and means controlled by the ice formation on the exterior of the evaporator for controlling the operation of said switch.

53. In a refrigerator having an evaporator. means for temporarily suspending the refrigerating cycle of the evaporator to render the same capable of defrosting, and

means controlled by the formation and melting of ice on the evaporator for controlling the said first named means.

54. In a mechanical refrigerator, 'means for defrosting the evaporator thereof automatically comprising means for temporarily suspending the refrigerating cycle to render the evaporator capable of defrosting. and means operable when temperature conditions are such that the evaporator is cleared of ice for automatically restoring the refrigerating cycle upon completion of defrosting.

55. In a mechanical refrigerator, means fordefrosting the evaporator thereof comprising means in the current supply line for opening the same temporarily to render the evaporator capable of defrosting. and means associated with the evaporator for controlling said first named means to restore the circuit in the current supply line and also restore the refrigerating cycle.

56. In a mechanical refrigerator including I an evaporator. means actuated by the formation and melting of ice on the evaporator for automatically suspending temporarily the refrigerating cycle to render the evaporator thereof capable of defrosting, and means for indicating the duration of the defrosting period.

In testimony whereof I aflix my signature.

CHARLES THOMAS HOFFMAN.

V v I DISCLAI MER 1,916,315.-0harles Thomas Hoflmaa, Washington, D. C. MEANS FOR AuroMA'rr- CALLY DEFROSTING REFRIGERATING UNI'rs.

Patent dated July 4, 1933.

' Disclaimer filed May 8, 1936, by the assignee, Lloyd M. Keighley. Hereby enters this disclaimer to claims 47, 48, 49, and50 of the specification.

[Qflioial' Gazette June 2, 1936.] 

